


You Came to Party

by EnRaa



Category: Undertale (Video Game)
Genre: Bad Jokes, Ecto-Genitalia (Undertale), Ecto-Penis (Undertale), Explicit Sexual Content, M/M, Oral Sex, Robot Sex, Tactile Sexual Interfacing
Language: English
Status: Completed
Published: 2020-11-09
Updated: 2020-11-09
Packaged: 2021-03-09 04:15:33
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 2,478
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/27478660
Author URL: https://archiveofourown.org/users/EnRaa/pseuds/EnRaa
Summary: “free drinks and food? that's exactly my kind of party.” Sans chuckled, and Mettaton smiled at him and shook his helm.“Well enjoy anything you'd like; Tonight's all about luxury and relaxation,” The mech purred. “I think even a laid back comedian like yourself can use some of that...”
Relationships: Mettaton/Sans (Undertale)
Comments: 4
Kudos: 25





	You Came to Party

**Author's Note:**

> I'm not gonna lie, I had more fun with the jokes in this than I had ANY right to. First fic for UT, although i feel like TF has primed me for Mettaton... I hope you enjoy!

The party had a good turn out, but Sans attributed that to the lack of new activities in the Underground. The same stuff happening day in and day out made a celebration of this magnitude seem like the best thing since the Resort itself had opened, and regardless of how silly the reason was, the party was igniting fun and hope, and their people needed that.

10,000 viewers for his television program was the reason Mettaton had thrown the party, 'as a thank you', he'd claimed, but the chance that the Barrier might be broken soon by the King was a cocktail that had most of the Underground pretty giddy and willing to use any reason to celebrate.

Sans had joined the party by accident, having forgotten about the flyers posted all over the Underground and arrived thinking he was performing his comedy routine. He walked into the lobby and was immediately swept into the stage room, where a server strode past him donning a blocky Mettaton costume and handed him a drink, and that was really all the convincing Sans needed to stay.

He'd parked himself at the bar and enjoyed a few more drinks, watching the crowd unwind to the loud music and drink their cares away. Some were dancing, most were holed up in corners socializing, and some even came to sit at the bar every now and then. Sans barely noticed as people sat down on either side of him, didn't notice at all as they'd peter off back into the crowd until someone else would take a seat.

“I really didn't expect you to be here tonight.”

Sans turned his attention to the newest monster to sit next to him, and found Mettaton watching him curiously, helm propped on his dainty servo as he leaned against the bar. “free drinks and food? that's exactly my kind of party.” Sans chuckled, and Mettaton smiled at him and shook his helm.

“Well enjoy anything you'd like; Tonight's all about luxury and relaxation,” The mech purred. “I think even a laid back comedian like yourself can use some of that...”

He decided to blame being a few drinks in for the way Mettaton's tone sent a shiver down his spine and made his marrow heat as magic began to stir. Instead of dwelling on it, he raised his glass and gave a curt nod. “to luxury and relaxation!”

Mettaton gave him an amused smirk before adding, “To rest and relaxation...” He mirrored Sans and took a sip of his own drink that had Sans' sockets widening as he sputtered.

“should you be drinking that?” He asked warily, watching the bot carefully for any sudden sparks or malfunctions, and Mettaton shot him a confused look.

“Why shouldn't I be?” He asked, seeming a little offended by that idea, and Sans shrugged his shoulders.

“you shouldn't be able to metabolize it, right?” He asked, and Mettaton's optics narrowed. “won't it mess up your internals?” Sans took a sip of his own drink and watched the mech pout and mull his words over. He had a hunch he was right if being called out brought such a strong reaction.

After a moment, the mech shifted, crossing his legs daintily on the stool and giving Sans a coquettish smile. “Well, what business are my internals to you, anyway?” He asked, his tone coy. Sans wasn't going to push him after deflecting him, but he definitely got the hunch that the bot was sizing him up for something if his tone and optics were anything to go by.

While Sans was sure fairly he was in no danger, he still downed the rest of his drink. Just in case. “i mean they're _your_ business, i just...uh, didn't know Alphys gave you the ability to drink... s'impressive if she did.” He said with a shrug, and Mettaton chuckled at him.

“She didn't,” He admitted, downing the rest of his own drink. “It...does mess up my internals. But I guess I get the same thrill out of it as you do when you get drunk from it.”

“i mean if you wanted some thrills, i'm sure someone wouldn't mind messing your internals up in another way.” Sans says without really thinking about it, and Mettaton's optics widen a bit before he smirks devilishly at him.

“Oh really...?”

Sans admittedly hadn't realized they'd been flirting, but as Mettaton shoved him back against the pillows and climbed up to straddle his legs eagerly, Sans could definitely see how his words were...misconstrued. Not that he minded.

“Darling, you're wearing far too many clothes,” Mettaton murmured as he pushed Sans' hoodie down over his shoulders, throwing it to the floor carelessly. “I want to see what I'm working with, here...”

Sans shuddered at the mech's tone as he pulled his shirt off, throwing it in the general direction he saw his hoodie fired to, and Mettaton's servos found his ribs, stroking over each one with more care than most non-metal partners ever cared to, and Sans choked out a gasp at the gentle tracing. “i'd say the same for you,” He let his hands stroke over the mech's hip plating, feeling how warm he was running and grinning. “show me what _i'm_ working with!”

Mettaton gave him a conflicted look. “I can't exactly take off my outfit, Sans, it's plating,” Mettaton began, and Sans shook his head.

“i know it's plating. lift it up,” Sans insisted as he traced over a seam in the plating on Mettaton's inner thigh that had him gasping and tilting his hips into the stimulation. “i know what i'm doing...” He assured the mech, and Mettaton gave him a shaky nod.

Sans was very thankful for having small hands. Working with machines, he was blessed to have small, thin phalanges that were perfect for getting at the delicate inner workings of his projects. Mettaton's thigh plating puffed out, as much as he could without disconnecting, and Sans had his fingers buried in the wiring and connectors, stroking over the metallic ball joint in the bot's groin that had him crying out and bucking into Sans' hand.

“Stars, you really know what you're doing...!” Mettaton gasped, splaying his thighs wider and letting Sans at every little crevice he could. Sans grinned up at him and slipped his fingers under the plating of his codpiece, stroking over the sensors hidden beneath and teasing the contacts of open ports with the sharp tip of a digit.

“i know my way around a fine piece of machinery,” Sans gave the bot a wink as he pinched a wire between two fingers, pulling at it just enough to create tension at the connection port that had Mettaton groaning deliciously.

“Mm, flattery will get you _everywhere_ , Darling...” Mettaton promised as he tugged Sans' hands off of him. He watched the bot shimmy down the bed a bit before tugging Sans' shorts off of him, throwing them behind him onto the floor before leveling his gaze to the magic pooling and taking form at Sans' pelvis. He brought a servo up and carefully traced over the ectoplasm, drawing a finger up the length of it as it formed a shaft. “How interesting...” He murmured softly as he took in the details, using his free servo to trace the curve of one of Sans' iliac crests, and Sans shuddered.

“oh, that's good...” He whispered, his hips lifting into the teasing touches. Mettaton took him in servo, stroking over his magic with confident, firm movements that made Sans wonder where he got his practice, but his thoughts were cut short when the mech leaned down and pressed his glossa to the shaft, dragging it up slowly until he reached the head, which he promptly took into his mouth.

Sans choked out a gasp at the sudden heat, trying his damnedest not to buck up into the bot's mouth. The heat the mech generated was beautiful enveloped around him, toe-curling pleasure coursing through him as the mech took him to the hilt in his mouth, the motion made slicker by the ectoplasm that hadn't taken form.

Mettaton pulled off the length for a moment, swiping his glossa over his lips and groaning. “Your magic...is playing hell on my sensors...” He said with a full-frame shudder. “It feels like it's shocking my oral sensors...” He said breathlessly, stroking Sans absentmindedly as he gazed up at him curiously.

“i might've added a little bit of charge to it to _spark things up_ a bit...” Sans admitted with a grin, and Mettaton groaned and rolled his optics.

“Oh, that's the worst!” Mettaton said, pinching at the crest he'd been stroking over and making Sans hiss as he chuckled.

“that pinch really _hertz_ , you know!” Sans said as his grinned down at the mech between his legs, and Mettaton frowned up at him. Sans' might've believed he was ruining the mood if the mech's optics weren't burning bright like they often did on stage when he was enjoying himself most.

“Must you do that _right now_?” The mech asked with a pout, and Sans just grinned wider.

“w _att_? i thought you liked my jokes!” Sans delighted in the way the mech's face scrunched up.

“You're insufferable!” Mettaton said firmly as he moved his servo from Sans' iliac crest down to his sacrum, right behind where his magic had formed, and rubbed his thumb in circles over the bone. “Only you would make puns in the middle of a blowjob.”

“guilty as _charged_!” The mech groaned dramatically and Sans smoothed a hand over the mech's hair, surprised at how soft it was. He used the tips of his fingers to glide over the mech's helm, pressing on sensors that had him moaning and pressing into the touch like a cat getting it's head scratched.

“Uhn, how do you know exactly where to touch...?” Mettaton growled softly, optics dim with pleasure as he lowered his helm back into Sans' lap and took him in his mouth once more.

Sans made sure to add a little more charge to his magic, and was rewarded for his efforts when Mettaton moaned wantonly around him. The vibrations were sinfully good on his magic, and every time Mettaton bobbed his helm and took him in he was mewling at the way the magic zapped at the sensors lining his mouth and throat.

The mech was rapidly heating up beneath his touch, and Sans could tell that Mettaton was headed towards an overload. Static was crackling over his plating and his optics began to glow bright, almost white as his charge rose.

He could feel himself racing towards that end with every moan and whimper Mettaton made around him. When hot digits wormed their way down to his pelvic inlet and scraped over the bone as they traced the arc, he couldn't contain his groan as he finally reached that delicious peak and came hard, Mettaton drinking down his magic eagerly and shuddering as it no doubt zapped harshly at his throat sensors and threw his charge into dangerous territory.

His frame overloaded, expelling the charge and making Mettaton tense up and cry out, though it was cut short when his vocalizer fritzed. He collapsed into Sans' lap, heavy and warm, and Sans reached a hand down to run through his hair again as the bot slowly onlined his systems.

“That was...” Mettaton sighed, vocalizer crackling and static-laced as he spoke.

“circuit-shorting? processor-blowing?” Sans suggested casually, watching the mech as he shifted into a more comfortable position next to him but staying pressed close enough to share the heat of his frame as they enjoyed their shared afterglow.

Mettaton smiled at him, tired but still dazzling. “All of the above.” He reached up to cup Sans' jaw and leaned forward to press a kiss to his mandible.

Sans didn't try to hide the way his skull grew hot from the mech's admission, instead just leaned up to press his teeth to Mettaton's lips. He felt the way the mech faltered for a moment before he pressed back, enjoyed the way he startled when Sans pressed his conjured tongue along the mech's bottom lip.

He opened his mouth and moaned when Sans' tongue pressed in, sliding teasingly against his own glossa and roaming over still buzzing sensors. They pulled apart slowly, and Mettaton sighed shakily.

“you alright there, M?” Sans asked with amusement, and the mech nodded slowly.

“It's just...intense, Darling,” Mettaton admitted breathlessly. “I don't think I've ever felt this good...”

“told ya there were better ways to mess with your internals!” Sans quipped, grinning playfully at the mech. “i mean any time you're feeling _bone_ -ly-” The sound of Mettaton choking out a giggle before catching himself made Sans pause, had him grinning impossibly wider and Mettaton couldn't hide his own smile behind his servos. Feeling invigorated, Sans propped himself up on an elbow and leaned a bit closer. “i guess there's gonna be a real _bone_ -us after my routines from now on, huh?”

Mettaton snickered, frame tensing in a way that Sans knew he was barely holding it together. “i really hope you're not the type to just _nut and bolt_ , though!” That one did it, and Sans watched excited as for the first time since auditioning at the Resort for Comedy Night, the robot laughed, beautiful and unrestrained.

“or maybe you're into that kinky stuff like _cog and bolt torture_ ,” He couldn't resist keeping it going when Mettaton looked so beautiful, so _real_ as he couldn't contain his laughter.

“Sans, Darling! _Please_ -” Mettaton pleaded and swatted at him breathlessly as he tried to compose himself.

“yeah, i should stop before you _charge me_ with _battery_ -”

“You're horrible!” Mettaton rolled onto his back, and Sans could tell he was still smiling even as he pressed his servos over his face. “Oh stars, I need a break...” He heaved, and Sans beamed at him.

“alright, but only 'cause i need to save some for next time.” He didn't really realize what he'd said until Mettaton looked at him with a mix of excitement and challenge, and he considered back-peddling, wondered if he'd made a wrong move, but then Mettaton rolled over to face him.

“Well I hope you plan on upping your game, Darling, because I'm going to be bored stiff if you try the same routine next week!”

Sans snickered. “oh, i think i can work with _stiff_ -” Mettaton's groan cut him off, followed by the mech lunging at him and pinning him down on his back.

“I'm going to have to shut you up myself, aren't I?” He challenged, and before Sans could answer he leaned down to kiss him. Sans wrapped his arms around the mech's neck and settled back against the bed, knowing they'd likely be there for a while.


End file.
